Process and apparatus for making pulp from fibrous material



June 14 1927.

1,632,467 F. K. FISH, JR

PROCESS AND APPARATUS FOR MAKING PULP FROM FIBROUS MATERIAL Filed July 1925 ATTORNEYS.

Patented June 14, l9 27. p I p I UNITED STATES PATENT oFF FREDERICK K. FISH, JR, OF SAN FRANCISCO, CALIFORNIA.-

PQROCESS AN D APPARATUS FOR MAKING PULP FROM FBBOUS MATERIAL.

' Application flledluly 15, 1925. Serial No. 43,851.

This invention relates to improvements in process and apparatus for making pulp from fibrous material and more particulary re-' lates to the circulation of the cooking liquor in the digester. j'

In methods now employed in cooking pulp, live steam is blown into the digester to cause circulation and to raise the temperature andpressureof the digesting liquor I '10 to raise the temperature of the material, and

increase the pressure in and around the material being cooked. The water of condensation from the steam dilutes the cooking li "nor to a very great degree, particularly in bringing the heat degree in the dlgester up through a relatively long range oftemperature. Moreover the reduction in. circulation, due to the decrease in the amount of steam entering the digester as the temperature and pressure increase to the maximum required,

and thereafter to the end of the cook, very materially delays the cook beyond the time that wouldbe required if the rapid circulation first attained, could be maintained throughout. When the digester becomes filled with liquor, it is necessary to remove liquor there rom, in order that steam may ,be admitted to maintain the required temperature as the cook progresses. Furthermore, owing to the reactions *taking place between the cooking liquor and the encrust-' ing substances of the fibrous material, the reactive properties of the liquor first penetrating the material, is quickly weakened and thus the cooking is further retarded.

In the sulphite process, particularly, to prevent burning or discoloration of ;the fibrous material,and to prevent weakening of the fibre, too high a temperature must be avoided, prior to thetime at which the protective properties of the cooking-liquor have been applied to the individual fibres.

In the sulphite. process, while the tem- 'perature is being raised, and throughout the cook, a considerable quantityof SO gas is liberated from the 'sulp'hite liquor, and this, as well as, valuable extractives of thematerial under treatment, collect above the charge in the digester. In the blow-01f as.

practiced with digesters now in use, the

, gases intermixed with the extractives are removed and their values are lost, hence these substances "do not exert their maximum cooking action on the material in the digester. These substances, essential'and valuable in the cooking operation, are ordinarily re1noved from the digester through the rehef line, and after cooling and separation, the S0 gas is returned to the liquor storage tank for use in a subsequent cook, thus los- 7 ing the effect of large quantities of heat,

space above the'charge in the digester and are thereafter returned to the lower portion of the digester to enrich the contained liquor cook. As in other methods, the valuable extractive properties of these fluids have been utilized up to the point of their removal from the digester, but by their return to with gases and and for further effective'use in the same the lower portion of the digester and their reuse in the same cook, there is a Very materially increased effect and added value of my improved process asa result.

This invention thus providesa-method of periodically and suddenly reducing the pressure in the digester, what may, for conyenience, be termed explosions occur and expel from the material being cooked, di-

gesting liquor which has been weakened 99 within the material, as well as melted, dissolved or decomposed portions of encrusting substances of the material. A liquor of increased strength in these extractive material properties is then .forced into the material being cooked, which, as a result of the explosionsf is naturally more susceptible to impregnation by the liquor. 7

In the accompanying drawing an 'appara- 'tus for operating the process is shown in 100 elevation and partly in section and my in- "vention will be best understood by reference thereto. V e v Tn'the' drawing, 1- indicates a digester of the usual type, having a steam inlet 2 and a I discharge outlet 3 at thebottom, and means 4 at the top for removing air from the ma: ,terial charged into the digester and reducing the pressure therein below atmospheric. Located adjacent to the digester is a pres sure tank 5 connected to the bottom part or the digester by a pipe (j having'avalve reducing the time of the cook, wherein by 6 lower end of the 10 part of the tank. In like manner the bottom of the pressure tank is connected to the upper part of. the digester, at a point below the level of the, digesting liquor by a pipe 10 having va-lves 11,11 and the pipe 10 is extended to connect with the pipe 6 as shown, a valve 21 being provided in the extension of the pipe 10. This connectlon makes it possible to. withdraw the liquor from the upper part of the digester'and return it directly to the lower part of the digester, or to the tank at will. This step is performed preferably in the latter stagesv of the cook when it is desirable to remove fluid from the space above the charge in the digester directly into the tank. 5 for use in a subsequent cook. The pressure tank is also connected at its upper end With the pipe 8 by means of pipe 12. having a valve 13.

Pipes 14 having valves 15 communicate with: the upper and lower ends of the pressure tank, to supply to orremove from the tank steam, gas or liquor. A. pump 16 is inserted 'in the pipe 6 to assist in circulating the liquor and gases in the. cooking operation.

.The pressure or accumulator tank 5 is large enough to hold suflicient fluid, which when removed-from the digester,-permits the necessary sudden reduction of pressure in the digester before the pressure in the tank.

0 becomes equal to thatin the digester. Air

5 within the fibrous material is removed from this tank before fluid is admitted from the digester, suitable screens 17 are provided on the various pipes entering the digester to prevent admission thereto of the fibrous material of the charge.

In carrying out the method, fibrous material is lntroduced into the digester, the

valve in the means 4 is opened and air is removed from the digester and change by means of a suction pump (not shown). Li uor'is then introduced into the digester and the cookstarted.

After-a: temperature, say about 225 F; has

' been reached in thedigester, an explosion is caused by a sudden lowering of pressure in the digester which permits the formation of steam, thereby causing an outflow of more or less spent liquor from the fibrous material and neces- 'sarily permitting an inflow of a more efiective liquor into such fibrous material. This explosion or sudden lowering of pressure is effected by opening the valves9 and 18 to permit the fluid in the form of gases and steam from the space in the upper portion produce unif ormity o part of the tank 5 to-force the liquor to of the digester to rush into the pressure tank 5. Moreover the valvesll and 11 are opened to cause liquor from the charge to flow into the tank, both gases and liquor, entering the tank at its lower end preferably in such a way as to mix the gases and liquor. The

-valves 9, 11 and 11*, are closed and the valve 7 opened, when the liquor enriched in the tank with the gases and volatile extractives are delivered to the lower part of the digester. This circulation is effected by means of the pump 16, and, if desired, may be assisted by-admitting steam under pressure into the upper partof the tank 5 through the connection 14. Moreover before the valve 7 is opened steam maybe admitted into the lower part of the tank5 to thoroughly agitate and heat the mixture of liquor and gases and to increase the pressure therein.

. As the cook progresses the temperature and pressure in the digester are raised to that required for effective cooking and the liquor uniformly strengthened is, circulated through the whole body of liquor and charge -in the digester.

This suddenrelease of pressure in the digester 1s carrled out periodically and each successive explosion opens up the structure of the material under treatment and separates individual fibres and removes melted,

dissolved ,and decomposed substances fromg within the fibrous material thus making it poss ble to more easily reach and act upon the lndlvidual fibres and to force a: greater amount of liquor into intimate contact with the material.

, The fluid withdrawn during the latter part of the cook from the top of the digester may be stored in the tank 5 for use in a succeeding cook. To effect this valves 7 9, and 11 are closed and valves 13 and 18 opened to permit the gases to flow into the upper portion of 'thetank.

In the early stages of the cook -I have found it advantageous to remove liquor from the lower part. temperature is highest and the liquor weakened by the steam admitted, into the tank and force it to the to of. the digester to concentration and of the digester, where the temperature, and circulation throughout the charge as promptly-as possible.

This is effected by opening valves 21 and permit liquor from the lower part of the digester to flow into the tank 5. N-alves 21 and 11 are then closed, valves 9 and 18 opened and steam admitted to the upper the top of the digester for the purpose described.

It will be apparent that I may conduct the operation at any desired suitable tempera ture and pressure and that there will be no condensation of the gases and vapors remgfied from the digester to the accumulator ta While I have described my invention in detail it will be understoo that various chan es may be made in the operation thereof w thout departing from the spirit of the invention, the'scope of which is defined in the following claims.

What I claim is I 1. The process of making puljp from fibrous material, consisting in removing air sure therein below atmospheric, then digesting said fibrous material in digesting liquor highly heated-and under pressure and with,

a space above the body of liquor, suddenly said space and in the liquor and directing the fluid flowing as aresult of such pressure reduction into a closed tank, raising the .temperature of the fluid in the tank and thereafter reintroducing the fluid from the tank into the digesting liquor to mix with said liquor for further use in the same cook.

2. The. process. of making pulp from fibrous material consisting in removing air from the fibrous material to reduce the pressure therein below atmospheric, then cooking said fibrous material in digesting liquor highly heated and under pressure, and with a space above the body of liquor, suddenly reducing the pressure correspondingly in said space and in the liquor, and directing only the fluid flowing as a result of such pressure reduction into a closed tank, from which air has been removed, and thereafter reintroducing the fluid to the bottom of the digesting liquor to mix with said liquor for further use in the samecoolt.

3. The process of making pulp from fibrous material consisting in removing air from the fibrous material to reduce the pressure therein below atmospheric, then submerging said fibrous material in heated digesting'liquor under pressure in a digester, periodically regulating the temperature and pressure of the digesting liquor to cause gas or liquor within the fibrous material to suddenly expand and thereby cause a separation of the fibres, recovering the fluid which alone escapes from the digester as a resultof the control of the temperature and pressure, and thereafter introducing the recovered fluid into the digester.

4. The process of making pulp, from fibrous material consisting in removing air sure therein below atmospheric, theusubmerging said fibrous material in and subjecting it to highly heated digesting liquor under pressure, suddenly reducing the pressure and temperature of the digesting liquor C surrounding the fibrous material to cause an outflow of the liquor from the fibrous material, thereby separating the fibres, r'e-' covering the fluid exclusively emitted by the sudden release of pressure and temperature,

from the fibrous material to reduce the pres reducing the pressure correspondingly in' pressure from the fibrous material to reduce the pres-- and thereafter introducing the recovered I .sure in the digester are again increased.

5.- The method of making pulp from fibrous material consisting in removing air from the fibrous material to reduce the pressure therein below atmospheric, then sub- ]ecting said fibrous material to digesting liquor highly heated and under pressure, suddenly reducing the pressure in the digester and recovering the fluid exclusively emitted therefrom in a closed tank and thereafter forcing the fluid frpm the tank into the lower part of the body-of the liquor-in the .digester to causea circulation of the liquor--in the digester.

6. The process of making pulp from fibrous material consisting in removing air from the fibrous material to reduce the pressure therein below atmospheric, then subgesting liquor under pressure, periodically reducing the pressure and temperature of the liquor surrounding the fibrous material and recovering the fluid exclusively released by such reduction of pressure and temperature', and thereafter introducing said re covered fluid to the digesting liquor for use in the same cook.

7. The process of making pulp from jecting said fibrous material to a heat difibrous material consisting in removing air y from the fibrous material to reduce the pressure therein below atmospheric, the'n cook ing said fibrous material in a heated digesting liquor ina digester, removing fluid from the digester above the material being cooked into a tank, and thereafter raising the temperature of the fluid so removed and returning it to the digester for reuse in the same cook 4 p J 8. The process of making pulp; from fibrous material consisting in removing'air from the fibrous material to reduce the pressure therein below atmospheric, then subjecting said fibrous material to highly heated digesting liquor under pressure, circulat ng the liquor and gases from the upper portion of the digester through a pressure tank, raising the temperature of said liquor in said tank and then introducing said liqthe tank to the body of liquor in the digester near its bottom, to thereby cause circulation of the. liquor in the digester' and ass ist in maintaining the temperature and pressure therein. 9. The process of brou's' material, consisting in removing air from the fibrous material to reduce the pressure therein below atmospheric, then sub-, merging said fibrousmaterial in heated d1-, gesting liquor under pressure, controlling the temperature and pressure to suddenly cause liquor within the fibre toexpand into steam nor from making pulp from space and directingthe fluid flowing. as a and separate the fibres, recovering the fluid which is alone permitted to escape from the digester as a result of the control of the temperature and pressure, and thereafter reintroducingthe recovered fluid into the digester.

10. The process of making pulp from fibrous material, consisting in removing air from the fibrous material to reduce the presheated and under pressure,

sure therein below atmospheric, then subjecting said fibrous material to heated digesting liquor under pressure, periodically reducing the pressure and temperature to cause a successive series of explosions within the fibrous material, to thereby cause an outflow from the fibrous material of weakened liquor containing decomposed or dissolved portions of the fibrous material, recovering the fluid so released and reintroducing it into the digesting liquor to cause an inflow of stronger liquor into the cells of the said fibrous material in the same cook.

11. The process of making pulp from fibrous material, consisting in digesting said fibrous material in digesting liquor highly heated and under pressure, and with a space vabove the body of liquor, suddenly reducing the pressure correspondingly in said space and in the liquor b releasing fluid from the space above the ho y of liquor, and directing the fluid flowing as a result of such pressure reduction into a'closed tank from which the .air has been removed, and thereafter reintro'ducin the fluid to the bottom of the digesting liquor to mix said fluid with said liquor for further use in the same cook.

. 12. The process of making pulp from fibrous material consisting in submerging said fibrous material in heated digesting liquor under pressure, periodically regulating the teniperature and pressure of" the digesting liquor to cause liquor within the fibre to periodically and suddenly expand into steam and separate the fibers, recovering the fluid which is alone permitted to escape from the digester as a result of the'control of the temperature and pressure, and thereafter introucing the recovered fluid into the digester.

13. The process of making pulp from fibrous material consisting 'in subjecting fibrous material to a heated digesting liquor in a digester, removing gases, vapors, and liquor from the upper portion of the digester into a tank, mixing the said gases, vapors an'd liquor in said tank and returning the mixture to the Iower portion of the digester for re-use in the same cook.

14. The process of making pulp from fibrous material, consisting in digesting said fibrous material in digesting liquor highly and with a space above the body of liquor, suddenly reducing the pressure, correspondingly in said space and inthe liquor by releasing fluid from said result of such pressure reduction into a closed tank, raising the temperature of the fluid in the tank above-that of the liquor in the digester and thereafter introducing the fluid from the tank into the digesting liquor to mix such released fluid with said liquor for further use in the same cook.

15. The process of making pulp from fibrous material, consistin in subjecting said fibrous material to a heated digesting liquor under pressure, periodically suddenly reducing the pressure and temperature of" thereby causing an outflow from the fibrous material of.

weakened liquor, containing dissolved and decomposed portionsof the fibrous material, recovering said fluid, raising its temperature and reintroducing it to the lower portion of the digester.

1'1 The method of making pulp from fibrous material, consisting in subjecting said fibrous material to digesting liquor highly heated and under pressure, suddenly reducing the pressure. in the digester and recovering the fluid exclusively emitted therefrom in a closed tank, and; thereafter forc-.

ing the fluid from the tank into the lower part of the body of the liquor in the digester .to cause a circulation of the liquor in the digester.

18. The process of making pulp from fibrous material consisting in 'subj ecting said fibrous material to digesting liquor under pressure and temperature above the'normal boiling point of the liquor, suddenly reducing the temperature and pressure of the liquor surrounding the substance by releasing gases and liquor from the upper portion of the digester to remove by force from the fibrous substance dissolved and decomposed portions of thefibrous substance, recovering and mixing the fluids so released, and thereafter reintroducin the mixed fluid so recov- 7 ered into the. ho y of'the. digesting li uor to recharge the same and cause said flui to circulate through the liquor in the same cook.

19.'The process of making p 1 from fibrous material, consisting in suiijecting said fibrous material to heated, di esting liquor under pressure, suddenly reducing the pressure of the liquor surrounding the substances by releasing liquor from the digester,

to remove by force from the fibrous substance, dissolved and decomposed portions of i in the same cook.

20. The process of making pulp from fibrous material, consisting in cooking said fibrous material in digesting liquor under pressure, in a digester, suddenly reducing the pressure of the digesting liquor to or about ill that of the atmosphere by releasing fluid from above the body of liquor in the digester and recovering said fluid, then cooking the fibrous substance at or about atmospheric pressure and thereafter reintroducing the recovered fluid into the body of digesting liquor to recharge the latter and cause circu ation of said fluid through-said liquor in the same cook.

21. The process of making pulp from fibrous material, consisting in cooking said fibrous material in digesting liquor which is enriched and heated duringthe cook by introducing thereto liquor containing valuable gases and other digestive extractives which have risen above the fibrousmaterial being cooked and which have been periodically separated from the digesting liquor and subjected to a mixing without permitting condensation or separation of such gases before being reintroduced to the digesting liquor.

22. An apparatus for making pulp which comprises a digester, a pressure tank adjacent-the digester, means to remove fluid and liquor separately from-the u per portion of the said digester and transf e'r them to the said tank, and means to circulate the said removed fluid and liquor from the tank to the digester.

'23. An apparatus for making pulpcom- 1 prising a digester, atank, a pipe adapted to communicate with the upper and lower portions ofthe said tank and the space above the liquor level in said digester, and a pipe connecting the lower portion of said tank with the upper portion of the 'digester at a point below the liquor level therein, said pipes having extensions connected with a further pipe line connecting the bottom of said tank with the lower portion of the digester, k

24. An apparatus as defined in claim .23

having means for removing air from the said digester, and valves arranged to permit a circulation and mixing of the gases, vapors and liquor in the digester.

25. An apparatus as defined in claim .23 wherein the said extensions are so connected with the said pipe line as to cause intimate mixture of gases, vapors and liquorv in transit between the upper and lower por-- tions of the digester.

26. An apparatus for making pul comprising a digester, a pressure tank a jacent said digester, a pipe connecting the lower portion of the digester with said tank; a second pipe connecting the lower portion of the tank with the upper portion of the digester and means to force liquor from the lower portion of the said tank to the upper portion of the digester.

27. An apparatus for making pulp, comprising'a digester, a pipe connecting a pump with the lower portion of the digester, a pipe connecting the intake of said pump with the upper portion of the digester at a point below the liquor level therein and a further pipe connecting the space above the liquor in the digester with the said intake pipe and adapted for the withdrawal and mixing 0 liquor, gases and vapors from the upper portion of the digester and for returning them to the lower portion of the said digester.

'28. The process of making pulp from fibrous material consisting in subjecting the fibrous material in a digester to heated digesting liquor with a space above the body of liquor, removing liquor from the upper portion of the digester and returning it directly to the lower part of the digester, while relieving fluid from the space above the liquor into an accumulator tank for use without separation in a subsequent cook.-

29. The process of making pulp from fibrous material consisting in cooking said fibrous material in digesting liquor which is enriched and heated during the cook by introducing liquor containing valuable gases and other digestive extractives which have risen above the fibrous materialbeing cooked and are ordinarily permanently removed from thedigester, without permitting condensation or separation of the said gases.

ture.

FREDERICK K. FISH, JR.

In testimony whereof I aflix my signa- I 

